dt-bindings: power: reset: Document ocelot-reset binding

Add binding documentation for the Microsemi Ocelot reset block.

Cc: devicetree@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>